Insulin, free fatty acids, and glucose response to intravenous glucagon following myocardial infarction

The response of plasma immunoreactive insulin (IRI), free fatty acids (FFA), and blood glucose to intravenous (I.V.) glucagon is evaluated in ten healthy subjects and in 22 patients following acute myocardial infarction (MI). Heparinized venous blood samples were drawn from patients and subjects in the fasting state and 2, 5, 15, 30, 60, 90, and 120 min after 1 mg I.V. glucagon. Healthy subjects showed a significant increase in insulin (peak at 5 min) and blood glucose (peak 15 min), and a persistent fall in FFA (nadir 90 min). In patients in the first week after suffering an acute MI, there was a significant elevation in fasting blood glucose whereas fasting insulin was low and FFA, normal. After glucagon administration, there was a pronounced rise in insulin and a significant rise in glucose and FFA. Six weeks after the acute MI, the mean fasting blood glucose reading showed a fall whereas insulin rose to normal range. Glucagon elicited a rise in insulin, glucose, and FFA. These results suggest that after MI the insulin resistance is a stronger influence than failure of insulin secretion. The relevance of these results in relation to use of glucagon in large doses in cardiogenic shock of MI is discussed.